I. Field
The present disclosure relates generally to communication and more specifically to pilot transmission in a wireless communication system.
II. Background
In a wireless communication system, a transmitter typically processes (e.g., encodes and symbol maps) traffic data to generate data symbols, which are modulation symbols for data. For a coherent system, the transmitter multiplexes pilot symbols with the data symbols, processes the multiplexed data and pilot symbols to generate a modulated signal, and transmits this signal via a wireless channel. The wireless channel distorts the transmitted signal with a channel response and further degrades the signal with noise and interference.
A receiver receives the transmitted signal and processes the received signal to obtain received data and pilot symbols. For coherent data detection, the receiver estimates the response of the wireless channel based on the received pilot symbols and obtains a channel estimate. The receiver then performs data detection (e.g., equalization) on the received data symbols with the channel estimate to obtain data symbol estimates, which are estimates of the data symbols sent by the transmitter. The receiver then processes (e.g., demodulates and decodes) the data symbol estimates to obtain decoded data.
The quality of the channel estimate has a large impact on data detection performance and affects the quality of the data symbol estimates as well as the reliability of the decoded data. The receiver can typically obtain a better channel estimate if the transmitter transmits more pilots. However, more pilots represent greater overhead that reduces the efficiency of the system.
There is therefore a need in the art for techniques to transmit pilots in an efficient manner to achieve good performance while reducing pilot overhead.